The problems of static electricity and Electrostatic Discharge (ESD) are well known and documented. In general, such problems arise from the occurrence of electrical events that cause the transfer of charge from one material to another creating a surge in voltage due to voltage potential differences between the two materials. The Electrostatic Discharge Association (ESDA), for example, cites industry experts as estimating that product losses due to static range from 8–33%. According to the ESDA, others have estimated the actual cost of ESD damage to the electronics industry as running into the billions of dollars annually. See http://www.esda.org/basics/part1.cfm.
In general, prior art methods of protecting components from ESD damage include some basic precautions such as proper grounding or shunting that will “dissipate” or discharge transient signals away from the device to be protected. Still other methods include the use of packages and handling techniques that will protect susceptible devices during transport and shipping. While such techniques have been effectively used to shield a product from charge and to reduce the generation of charge caused by any movement of the product within the container housing the device to be protected, they have not completely eliminated the risk of damage attributed to such disturbances. Moreover, it is well known that more modern devices operating in the higher frequencies (GHz and above) using submicron line widths are more susceptible to damage which cannot be overcome using such methods.
Components designed to react to ESD events and provide a discharge path to ground are known in the arts. For example, U.S. Pat. No. 6,172,590 entitled “Over-voltage protection device and method for making same” to Shrier et. al (Ms. Shrier is a co-inventor to the '590 patent. The '590 patent is not commonly assigned to this application) describes a discrete electrical protection device that utilizes a gap between two electrically conductive members attached to an electrically insulating substrate. According to the '590 patent, the electrical protection device can be either surface mounted or built with through-holes for accommodating leads on an electrical connector. The '590 describes and claims methods for making an electrical protection device that includes an electrically insulating substrate.
U.S. Pat. No. 6,310,752 entitled “Variable voltage protection structures and method for making same” to Shrier et. al (Ms. Shrier is a co-inventor to the '752 patent. The '752 patent is not commonly assigned to this application) describes and claims a variable voltage protection component that includes a reinforcing layer of insulating material having a substantially constant thickness embedded in a voltage variable material. According to the '752 patent, the reinforcing layer defines a uniform thickness for the variable voltage protection component resistive to compressive forces that may cause a reduction in the clamp voltage or a short in the voltage variable material. The '752 patent also describes methods for making such a variable voltage protection component.
Prior art protection components, such as those incorporating the teachings of the '590 patent and the '752 patent, have been successfully made and used. Generally, such components utilize a couple of electrodes with some type of surge material interspersed between the electrodes. One electrode provides the transient signal input terminal while the other provides the discharge path to ground. A support layer known as the substrate or reinforcement layer is used to provide the necessary stiffness permitting the component to be surface mounted or through-holed.
Such prior art protection components, however, suffer from several limitations attributed to the requirement that a substrate or reinforcing layer be used. Specifically, the use of a substrate adds significantly to the component's overall size and cost. In addition, the relatively large size and profile of such prior art protection components makes their use impractical in tight spaces where board space is limited. Moreover, since the substrate material is a primary expense in the manufacture of such components, the use of prior art protection components on a widespread basis can be cost prohibitive. An example of such an application would be a multi-pin connector where ideally each pin would be protected from ESD events that could damage a device coupled to the connector. In such an application, a prior art ESD protection component could not be cost effectively used on each pin and, in most situations, would occupy too much board space and be too thick to be practical.
As electronic devices become faster and smaller, their sensitivity to ESD increases. ESD impacts productivity and product reliability in virtually every aspect of today's electronics environment. Many aspects of electrostatic control in the electronics industry also apply in other industries such as clean room applications and signal line proliferation.
Therefore, a need exists for a cost effective protection component that can be more widely used across a wider range of applications. A method of cost effectively manufacturing such a component would provide numerous advantages.